Vapor-electric device and method of making the same



Nov. 4, 1952 e. LEWIN ETAL 2,617,070

VAPOR-ELECTRIC DEVICE AND METHOD OF MAKING I'THEI'SAME Filed Sept. 12, 1951 4 ATTORNEY Patented Nov. 4, 1952 VAPOR-ELECTRIC DEVICE AND METHOD OF MAKING THE SAME Gerhard Lewin, Maplewood, and Ernest A. Goldman, Bloomfield, N. J., assignors to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application September 12, 1951, Serial No. 246,296

Claims.

This invention relates to vapor-electric devices, such as are generally known as ignitrons.

A recent development in this art is the provision of a sponge cathode consisting ofa material of porous character which will absorb mercury or the like and constantly present a mercury-wet surface toward the ignitor and anode in an ignitron. In the usual mercury-pool type of ignitron, the ignitor pentrates below the surface of the pool and thus insures conductive contact between the ignitor and mercury. In the ignitrons with a sponge cathode, however, the contact between the sponge and ignitor is one of engagement of the end of the ignitor on the sponge surface. It has been found necessary to apply pressure on the ignitor toward the cathode to assure conductive contact at the point of engagement. The present invention contemplates an assured contact of ignitor and sponge cathode.

An object of the invention is to assure such contact without resort to spring pressure or weights.

Another object of the invention is to provide constant and unalterable contact of ignitor and cathode.

A further object of the invention is to fabricate the cathode and ignitor with predetermined area of contact.

A still further object of the invention is to provide an ignitor embedded in the sponge cathode during fabrication and permanently fixed thereto.

Other objects of the invention will appear to those skilled in the art to which the invention appertains as the description proceeds, both by direct reference thereto and by implication from the contact.

Referring to the accompanying drawing, in which like numerals of reference indicate similar parts throughout the several views:

Fig. 1 is a vertical central sectional view of an arbitrarily selected ignitron showing our invention included therein.

Fig. 2 is a view showing the cathode and the igniter in cross section.

In the specific embodiment of the invention and associated ignitron construction illustrated in the drawing, there is shown a cylindrical casing ID of steel or other sturdy material having a bottom 12 integral therewith and a top header [3 sealed at the upper rim of said casing to provide a closed envelope adapted to be evacuated.

The header provides appropriate lead-in seals l4, l5 for electrode leads I6, I! respectively for an anode l8 and ignitor 19 within the casing. The lead-in seals each include a glass or other insulating sleeve 20 by which the leads are kept electrically distinct from each other and from the casing. The anode I8 is located toward the top of the casing, well above the bottom wall l2, whereas the ignitor I9 is located below the anode and is directed toward and terminates at its bottom in the vicinity of said bottom wall.

In said casing I 0, at the bottom thereof juxtaposed on the bottom wall [2, we provide a cake or body 2| composed of a porous material which has the property of a sponge absorptive and/or adsorptive to mercury or other reconstructable liquid cathode material, and while we prefer to use metal for the purpose, we do not confine ourselves thereto. Such metals as sintered iron, sintered molybdenum, sintered ruthenium, sintered platinum and the like, singly or in any combination thereof, have been found to be acceptable cathode sponge materials. The cake or sponge 2| is flat and occupies only a small part of the casing, and preferably diametrically extends across the bottom of the casing or envelope to the cylindrical wall thereof with which it may make frictional engagement for retention in place.

Mercury or other reconstructable cathode material is applied to the sponge body 2| to extent that said body will absorb the mercury or the like without any excess remaining on the surface. One manner of thus charging the sponge body with mercury is to cleanse the sponge material until sufiiciently clean to be wetted by mercury and then apply an excessive amount of mercury in the casing. whereupon the sponge will immediately fill with mercury, after which the free mercury which is not absorbed into the sponge can be poured off. The sponge body or cake 2| with the absorbed mercury constitutes the oathode of the ignitron.

The principal feature of the present invention is the unification of sponge body 21 and ignitor l9 so that the ignitor has fixed position and positive engagement with the sponge body. The preferred accomplishment of this desideratum is to bury the lower end of the ignitor in said sponge body with the major portion of the ignitor projecting perpendicularly upward from the top surface of said body. It is furthermore preferred that the ignitor have inseparable engagement with the sponge body and thereby assure good electrical contact of a considerable surface of the ignitor with the cathode. One mode of acwhich is sintered in the compressed shape and constitutes a firm, porous body in consequence ofv the initial material used and treatment thus ap-' plied. A pressure of one totwo tonsper square inch and sintering temperature of approximately 1800 F. have proven satisfactory With particles of iron and other materials hereinbeforeflisted.

As an example of means for-compressing the multitudinous particles or units into cake formation, Figs. 3 and 4 show a hollow die 22 the inside diameter of which is made'to correspond, with compensation for shrinkage, to the desired diameter of the cathode body to be formed. The bottom end of the hollow die is closed by. aseca tional lower die -23, and an upper die, 21 is,pr'ovided adapted to be'loweredinto the hollow die for applying th desiredpressure'to, materiaI'iZb.

poured or otherwise introduced into the hollow. die. The lower die '23 has a properlyjlocated socket 25 therein for reception of a preformed.

ignitor'lB. The socketis oflappropriatedepth'to receive the major portion of the'ignitor which,

is placed in said socket upside down so that what, is normally the bottom end of the ignitor'in'use protrudes upwardly from the itop surfaceof the.

lower die. The amount of protrusion is-madeto agre with the desired depth of ultimate burial of the ignitorin'the cathode sponge'bocly.

The method of fabrication herein disclosedcontemplates first introducing a small amountof. cushioning material 2'! in thebottomlofsocket 26 having thetwo-fold functions vof conforming the bottom of-the socket to-thesurfaoeconfigurae tion of the ignitor end to prevent cracking orl shipping the ignitor when pressureis applied, and to also prevent theignitor from sticking ..to the bottom of the socket as. a .result of applied pressure. The amount of protrusion .of the ignitor can'be varied by appropriatevariation.or amount of material? 21 .introducedlinto'. socket; 26. While numerous materials are usable for forming the cushion, it is convenient toutilizena small quantity of the same material of whichthe sponge cathodev is to be composed, andthus. avoid possible contamination of the ignitorwby intro: duction of some deleterious ingredient.

After the cushioning material 21 isintroduced into socketifi, thelignitor [.9 isinserted top end downward into contact with the cushioning-material and with the-otherend protruding-above 4 the top face of the lower die. Next a measured amount of sponge-forming material 25 such as finely divided iron, molybdenum and so forth as above described, is introduced into the hollow die on top of the lower die and completely surrounds andncovers the protruding end of the lgnitor. Then the :.top -"die is forced down underathe desired pressure of one or two tons per square inch thereby compressing material 25 into a compact,

though spongy, firm cake with an end of the ignitor embedded therein. This cake, with the ignitor therein, is then sintered at approximately 1800 F. The .formed. cake is removed from the dies with the embedded ignitor therewith, before sintering. Dueto the compression applied to the materialin forming the cake, the ignitor is tightly gripped therein. The sintering operation obtains some shrinkage'ofthecake and consequently the ignitor is even more tenaciously anchored in the cake or sponge body in the completed assembly, andthus the ignitor ispermanently attached to and'has an end buried in the sponge body.

Itrmay be noted, that the preferred construction, of ignitor utilizes anintegral carbon head or upper end portion 23 which is morereadily bored with a hole .30v for reception of the lead-in rod I! than the usual ignitor, Which/for sponge cathode use may consist of boron carbid and alumina.

Weclaim:

1. In combination, a. porous cathode body, and an ignitor secured tosaid body.

.2. In combination, a porouscathode body, and an ignitor having an :end embeddedin said body in tight contact therewith.

3. In combination, a porous'cathodebody, and an ignitor having an end embeddedpermanently in and gripped bysaid body.

4. A' method of manufacture of, a combined cathode and ignitor comprising preforming an ignitor and simultaneously compressing other material around an endmargin of said ignitor and into its ultimate shape of cathode body.

7 5. A method .of manufacture of a combined cathode and ignitor comprising preforn'iing. an ignitor and simultaneously compressing other material around an endmargin of .saidignitor and intoits ultimate. shape of cathode body, and thereafter sintering the said body with the ignitor buried at itsv end therein, thereby bothconditioning thebody for use and. shrinkingit into tight.

engagement with the ignitor.

No referencescited. 

